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Re: Vermont Granite Worker Cohort

To the Editor:

I found the recent paper “Reducing healthy worker survivor bias by restricting date of hire in a cohort study of Vermont granite workers” by Applebaum, Malloy and Eisen to be of great interest, especially as my colleagues and I are currently conducting a mortality study of Vermont granite workers. The cohort used by Applebaum et al., which was assembled and followed by W.G.B. Graham and J. Costello, has been used in several previous studies.(1-3) Our current study includes this cohort, but we have endeavored to identify workers who were not in the Graham cohort because they did not have a chest X-ray as part of a medical surveillance program. From our efforts to date, it appears that they constituted about a third of all workers. Because the exclusion of these individuals may have introduced considerable selection bias, the results of all studies based on the Graham cohort should be interpreted with caution.

Sincerely,

Pamela M. Vacek

References:

1. Costello J, Graham WGB. Vermont granite workers’ mortality study. Am J Ind Med 1988; 13:483-97.

2. Graham WGB, Costello J, Vacek PM: Vermont granite mortality study: an update with an emphasis on lung cancer. J Occup Environ Med 2004; 46:459-66.

3. Attfield MD, Costello J. Quantitative exposure-response for silica dust and lung cancer in Vermont granite workers. Am J Ind Med 2004; 45:129-38.